Limulus amebocytes are normally discoid and highly granulated. However, minute amounts of endotoxin cause cellular degranulation and lysis, followed by the formation of an extracellular gel. While the mechanism of gel formation is to a large extent understood, mechanism of endotoxin mediated degranulation and lysis of amebocytes remain unclear. This study is directed toward the elucidation of the membrane structure of the amebocyte and the analysis of the events that lead to the degranulation and lysis of the amebocyte triggered by endotoxin.